[Hematological disturbances in subclinical hypothyroidism and their dynamics during substitution therapy]

The aim of the study was to estimate dynamics of hematological disturbances in autoimmune thyroiditis and subclinical hypothyroidism (SH) during substitution therapy and without it and to elucidate factors promoting successful correction. The control group included 36 women, 60 others had SH. They were matched for age, BMI, free T3 level but differed in TSH (1.8 +/- 0.81 vs 7.0 +/- 3.41 mcunits/ml, p < 0.001) and T4 (p < 0.001) levels. 53 women with SH were followed up for 1 year; 18 of them were not treated (subgroup A) while 35 were given levothyroxin (subgroup B). The following red blood parameters were measured hemoglobin (Hb), ferritin, mean erythrocyte volume, erythrocyte Hb content and concentration, blood iron (Fe) level. SH was characterized by decreased (compared with control) Hb levels (125.8 +/- 13.75 and 133.2 +/- 9.12 g/l, p = 0.005), erythrocyte volume (p = 0.022), Hb content per erythrocyte (p = 0.001), ferritin (24.6 +/- 20.56 vs 36.6 +/- 30.66 mcg/l, p = 0.02), and Fe (p = 0.001). The frequency of anemia (28.3 vs 11.1%, p = 0.039) especially microcytic anemia (p = 0.035) increased A year later women of subgroup A showed further decrease in ferritin level (p = 0.011) and increase in anemia frequency (p = 0.016): microcytic (p = 0.23) and normocytic (p = 0.015). In subgroup B, the frequency of anemia decreased (p = 0.001) while ferritin, Fe and Hb levels slightly increased (p > 0.05). The best effect of therapy and highest rise in ferritin level were documented in younger patients (p = 0.06), in the absence of obesity (p = 0.003) and at the low initial ferritin level (p < 0.001). In regression analysis, ferritin level (094 [0.89; 0.99], p = 0.035) proved the most significant predictor of therapeutic effectiveness. SH was characterized by Fe deficiency, tendency to microcytosis and anemia that progressed in the absence of therapy. Substitution therapy promotes normalization of hematological problems especially in young and non-obese patients. Sideropenic syndrome suggests potential benefits of levothyroxin therapy and may be regarded as an additional indication for its prescription.